Rapid Assessment of Olfactory Sensitivity Using the “Sniffin’ Sticks”

Abstract

Introduction Assessment of olfactory performance is of high clinical interest in the contexts of smell loss as well as neurological diseases, and recently gained attention in obesity research. Available olfactory tests, especially for assessing olfactory sensitivity, are time-consuming and require high cognitive capacity. Therefore, we aimed to establish a short procedure for reliably testing olfactory sensitivity using a subtest of the BSniffin' Sticks^battery. Evaluation criteria are test duration, validity, and test-retest reliability. Methods In a preliminary study using a within-subject repeated-measures design, we measured olfactory sensitivity for n-butanol in 20 young and healthy participants. We compared sensitivity obtained with three different measures during two sessions in a pseudo-randomized order: a standard single-staircase three-alternative forced-choice procedure with seven reversals (SSP_7); an abbreviated version with five reversals (SSP_5); and an ascending presentation of 16 dilution steps from lowest to highest odor concentration (brief ascending procedure, BAP). Results Compared to the SSP_7, the BAP was 51%, and the SSP_5 26% shorter in duration. Both the BAP and SSP_5 scores were highly correlated with the SSP_7. The test-retest reliability in all three tests was similar to that typically reported in olfactory research. Conclusion The abbreviated tests are valid measures of olfactory sensitivity. Especially, the BAP is as reliable as the standard method, but remarkably faster and easier to perform. Implications Thus, the short procedures bear potential for both research and clinical practice, especially for complex study designs with time constraints on olfactory testing and for patient populations with attention deficits.

Insulin Resistance Is Associated with Reduced Food Odor Sensitivity across a Wide Range of Body Weights

“…To obtain similar perceived intensity of the three odors, chocolate pens were filled with highest 1% and lowest 31 ppm and grass pens were filled with a highest odor concentration of 4% and the lowest of 1.22 ppm, both in a similar ratio of 1:2 (pilot study, n = 10). We then applied the short single staircase procedure as described in Poessel et al [45] to determine odor thresholds.…”

A New Method for a Shorter and Valid Assessment of Olfactory Threshold in Repeated Measurement Designs Based on the Sniffin’ Sticks Test

“…To a priori determine the minimum number of participants required, we used G*Power software (Faul et al 2007). Informed by previous results (Croy et al 2009;Pössel et al 2020), we set the expected correlations of the original threshold with our INFOUR procedure to r = 0.70, which is considered as large effect size according to the classification of Cohen (1988). The optimal sample size to statistically ensure a high effect with α = 0.05 and 1-β = 0.80 is calculated to n = 11 participants.…”

“…For the second trial, one group repeated the original version (group 1) again while the other received the INFOUR version as outlined in the introduction (group 2). The break in between was set to 15 min, which was in line with (Sijben et al 2017) or even longer than previous related study designs (Besser et al 2019;Pössel et al 2020).…”

“…This results in a promising time reduction of 51% with a correlation of r = 0.76 to original Sniffin' Sticks threshold test and retest-reliability of r = 0.68 within one week. Additionally, Pössel et al (2020) simulated another shortened threshold score test. The authors performed the original Sniffin' Sticks threshold test with seven reversals, but calculated the score by the last two out of the previous five reversals.…”

“…Therefore, the use of such brief procedures is and d) the wide steps method (WSM, Croy et al 2009). An X indicates a correct detected target pen in a triplet, a minus indicates an incorrect detected target pen; arrows pointing up and down refer to steps in higher or lower directions; red dashed circles mark the trials that are included in the score calculation recommended when larger group differences are expected (Pössel et al 2020). This is a potential disadvantage for repeated measurement designs if only subtle effects are of interest.…”